In the existing telephone answering machines, if the user wishes to listen to the messages through the handset, he must manually operate a button or a switch. A significant disadvantage of this feature is that if the switch is inadvertently left in the handset playback mode, any one who is unfamiliar with the switching mechanism will not be able to respond to the incoming calls. Additionally, existing telephone answering machines cannot handle the transitions of the message playback from speaker to handset automatically, without user-intervention.
In the patent to D'Agosto III et al., U.S. Pat. No. 4,790,002 a telephone answering machine has a telephone/speaker phone combination that allows a separate Record/Playback Module. The device forms a unit having a telephone answering machine and dictation machine. The patent discusses the use of the handset for recording messages, but there is no mention of the use of the handset in play back.
In the patent to Shapiro et al., U.S. Pat. No. 4,760,593 is described a personal alarm system which incorporates a speaker phone so as to permit hands free operation and remote activation via a switch on a hand held unit. It will react differently to the switch depending on whether or not the line is ringing. The following passages explain this aspect of the invention in more detail:
In the event of subscriber inactivity, or in the event a subscriber activates a "help button" to indicate assistance is required, the subscriber station transmits an alarm message containing subscriber identification information over a communications link to the central monitoring station. (Column 1, lines 46-51) PA1 In the speaker phone disabled state, the telephone may be answered by a subscriber in the conventional manner by lifting the telephone handset or, as explained below, by activating a "help button" while the phone is ringing. . . . . Upon the occurrence of these concurrent events, the subscriber station produces a speaker phone off hook condition, and activates the speaker phone so as to permit the calling party and the subscriber to converse without the need for the subscriber to lift the telephone handset. (Column 3, lines 8-29)
Although this device switches during message playback, it uses it for a purpose completely different from that of the present invention.
GTE Model 6010-- This product is a telephone answering machine that uses a manual switch to allow the user to listen to messages over the handset. Our invention provides substantial improvement over this product by performing the switching automatically.